Auxiliary power unit for a hybrid electric vehicle

ABSTRACT

An auxiliary power system includes an engine balance system, an integrated alternator/starter, a thermal management system, noise-vibration-harshness control system, an emissions/fuel economy system, an APU master control unit, and a vehicle control system.

This is a Divisional application of application Ser. No. 08/376,043,filed Jan. 20, 1995, now U.S. Pat. No. 5,469,820, which is a FileWrapper Continuation application of Ser. No. 08/093,536, filed Jul. 15,1993, abandoned, which application(s) are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to an internal combustion engine basedauxiliary power unit for a hybrid electric vehicle.

Background of the Invention

IC engine powered vehicles have been commercially marketed for about onehundred years and dominate the vehicle industry. Despite theirwidespread use, gasoline fueled IC engines have been associated withenvironmental problems from exhaust emissions and exhibit low fuelefficiency under light load operation and high emission under transientloads.

Electric vehicles are an alternative to combustion engine poweredvehicles when minimizing vehicle exhaust emissions is a primary goal.However, pure electric vehicles developed to date have limited range ofoperation without battery recharging. Typical limitations also includespecial electric power requirements for recharging the vehicle'sbatteries.

Because of these pure electric vehicle shortcomings, efforts have beendirected toward the development of hybrid electric vehicles. Hybridelectric vehicles are viewed as a workable compromise betweenconventional engine powered vehicles and pure electric vehicles. Thehybrid electric vehicle in this invention is powered by batteries, andan auxiliary power unit comprised of an IC engine driven electricalternator. This combination increases driving range compared with pureelectric vehicles while achieving improve fuel economy and lower exhaustemission when compared to conventional technology.

However, current hybrid electric vehicles have several limitations inthe areas of noise and vibration control, emission control and thermalmanagement. These problems limit the chance for commercial success. Amajor concern in a hybrid electric vehicle are annoying vibration causedby pitch, yaw, and roll torques, which are generated by cyclicirregularities of IC engines. Another concern is the high noise level ofthe APU when compared with electric motors. Yet another concern isthermal management of the IC engine and alternator when located in arestricted space. Still another concern of a hybrid electric vehicle isthe emission control requirement. More efficient combustion andeffective emission control are required to have a practical hybridelectric vehicle that meets future emission standards.

The present invention addresses these and other shortcomings, which whencombined together into a highly integrated APU system by optimizeddesign, minimizes concerns and limited acceptance of prior art.

SUMMARY OF THE INVENTION

The present invention relates to an auxiliary power unit for a hybridelectric vehicle, which minimizes vibration and noise caused by cyclicengine torques, cyclic alternator/starter torques, and cyclic forcesfrom the engine and alternator/starter assembly.

A preferred embodiment also minimizes vibration and noise caused byexhaust, induction, and noise radiation from the engine andalternator/starter assembly of the auxiliary power unit.

In one embodiment of an auxiliary power unit, a rotor of analternator/starter is mounted on a balance shaft which is coupled to anengine crankshaft by a gear assembly. The balance shaft/rotorcombination rotates in a direction opposite to that of the crankshaft.The engine and the alternator/starter are configured and arranged tohave a zero net angular momentum which results in the auxiliary powerunit not imparting any primary pitch, primary yaw, or roll torques toits mounting structure. In particular, the rotating parts in theauxiliary power unit are configured and arranged to have a zero netangular momentum, which eliminates roll torques.

One embodiment of an auxiliary power unit for a hybrid electric vehiclegenerally in accordance with the principles of the present inventioncomprises:

a IC engine driving a crankshaft;

a balance shaft;

gear means for interconnecting the crankshaft to the balance shaft tocause the balance shaft to be rotated in a direction opposite to that ofthe crankshaft;

an alternator/starter positioned on an end of the balance shaft; and

wherein a net angular momentum of the auxiliary power unit is zero.

One embodiment of an auxiliary power system includes the auxiliary powerunit, a sensor unit for sensing the energy level of batteries so thatthe auxiliary power unit automatically starts operating when the energylevel of the batteries is low. An APU master control unit controls theoperation of the auxiliary power system to meet the power requirement,noise reduction requirements emissions requirements, or otherrequirements of the hybrid electric vehicle.

One embodiment of a hybrid electric vehicle comprises:

a battery assembly providing electricity to the hybrid electric vehicle;

auxiliary power unit, electrically connected to the battery assembly,for charging the battery assembly when the battery assembly needscharging;

noise control means for controlling noise from the auxiliary power unitwhich affects exterior and interior vehicle noise levels;

vibration control means for controlling vibration levels of the vehicle;

cooling control means for cooling the alternator/starter and the engineof the auxiliary power unit, and for ventilating air from the auxiliarypower unit, the cooling control means including an alternator/starteroil sealing means for preventing cooling oil from leaking into thealternator/starter causing viscous drag, the cooling control systemusing a shared engine lubrication system;

emission control means for controlling the exhausting of exhausted gasesfrom the auxiliary power unit;

battery charging means for providing initial engine cranking power andbattery charging power;

electronic engine control means for controlling the battery chargingmeans and an engine operating parameters of the hybrid electric vehicle,and reduced maintenance by elimination of external belts and pullies,and limitation of contact of the alternator with water and other coolingcontaminates by a sealed design using oil cooling; and

wherein the auxiliary power unit comprises:

a IC engine driving a crankshaft;

the alternator/starter positioned on an end of a balance shaft;

gear means for interconnecting the crankshaft to the balance shaft tocause the balance shaft to be rotated in a direction opposite that ofthe crankshaft;

wherein a net angular momentum of the auxiliary power unit is zero.

In one embodiment of a hybrid electric vehicle in accordance with theprinciples of the present invention, an auxiliary power unit isinstalled in the hybrid electric vehicle. All shaking forces as well asprimary pitch, primary yaw, and roll torques produced by the auxiliarypower unit are eliminated.

In yet another embodiment, a hybrid electric vehicle includes a noise,vibration, and harshness attenuation system so that the noise,vibration, and harshness of the auxiliary power unit are attenuated andmasked.

In one embodiment, a hybrid electric vehicle includes an emissioncontrol system so that fuel is efficiently combusted, and exhaustedemission are effectively reduced.

In one embodiment, a hybrid electric vehicle includes a cooling controlsystem. The cooling control system includes water cooling system and oilcooling system to reduce the high temperature created by the auxiliarypower unit.

In one embodiment, a hybrid electric vehicle includes a battery chargingsystem, which includes a three-phase bi-directional inverter which isinterconnected to the alternator/starter providing initial enginecranking power and controlling alternator/starter output power, current,and voltage.

In one embodiment, a hybrid electric vehicle includes a propulsioncontrol system for monitoring and controlling operation of the auxiliarypower unit.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and forming a part hereof. However, for a betterunderstanding of the invention, its advantages and objects obtained byits use, reference should be had to the drawings which form a furtherpart hereof, and to the accompanying descriptive matter, in which thereis illustrated and described a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings in which like reference numerals and letters generallyindicate corresponding parts throughout the several views:

FIG. 1 is a perspective view of an embodiment of an auxiliary power unitin accordance with the principles of the present invention;

FIG. 2 is a view similar to FIG. 1 with portions of the auxiliary powerunit housing removed to illustrate internal parts;

FIG. 3 is a transverse cross-sectional view of the auxiliary power unit;

FIG. 4 is a cross-sectional plane view of the auxiliary power unit;

FIG. 5A is a cross-sectional view of a rotor of an alternator/starterpositioned on the end of a balance shaft;

FIG. 5B is a cross-sectional view along the line 5B--5B in FIG. 5;

FIG. 5C is a cross-sectional view along the line 5C--5C in FIG. 5;

FIG. 5D is a partially enlarged cross-sectional view of FIG. 5;

FIG. 5E is a partially enlarged cross-sectional view of FIG. 5 beingtransactionally rotated 45 degrees;

FIG. 5F is a cross-sectional view of a second embodiment of the rotor ofthe alternator/starter positioned on the end of the balance shaft;

FIG. 5G is a cross-sectional view of a second embodiment along the line5G--5G in FIG. 5F;

FIG. 6A is a perspective view of the auxiliary power unit disposed in anenclosure which is opened for purposes of illustration, a ventilationsystem being connected to the enclosure for ventilating the auxiliarypower unit;

FIG. 6B is a graph of APU engine noise level vs. Frequency;

FIG. 6C is a graph of noise levels in a frequency domain;

FIG. 6D is a graph of interior noise level (dB) vs. vehicle speed (mph)of a typical vehicle;

FIG. 6E is a graph of exterior noise level (dB) when the vehicle isstopped in a typical vehicle, such as '93 Caravan;

FIG. 7A is a schematic diagram of an embodiment of a cooling systemutilized with the auxiliary power unit;

FIG. 7B is a schematic diagram of another embodiment of a cooling systemutilized with the auxiliary power unit;

FIG. 7C is a partially schematic diagram of the reversedalternator/starter cooling system;

FIG. 8 is a block diagram of a hybrid electric vehicle system inaccordance with the principles of the present invention;

FIG. 9 is an electrical schematic diagram of an inverter for a batterycharging system;

FIG. 10 is a noise, vibration, and harshness control system;

FIG. 11 is a block diagram of a hybrid electric vehicle control system;

FIG. 12 is a graph of APU engine speeds vs. time in a battery chargingsystem; and

FIG. 13 is a block diagram of the battery charging system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hybrid Electric VehicleGeneral Information

In FIGS. 1 through 4, there is shown an embodiment of an integratedauxiliary power unit 80 in accordance with the principles of the presentinvention. In the embodiment disclosed, the auxiliary power unit 80 is avery compact unit including a three-cylinder combustion engine 84 and analternator/starter 86 disposed in a common housing 82. Thealternator/starter 86 is mounted on a crankshaft of the combustionengine 84. It will be appreciated that the auxiliary power unit 80 mightinclude combustion engines having different numbers of cylinder(s),e.g., one, two, three, four, etc. The auxiliary power unit 80 has a verylow profile. In addition, it has no external belts and has no flywheels.

In one embodiment the combustion engine 84 might be a three-cylinder,four-cycle engine having an inline configuration. The engine might havethe following detailed features: spark ignition, 74×78 mm bore & stroke,9.75:1 compression ratio, in-head combustion chamber with 10-20% squisharea, closed loop sequential port fuel injection, A/F ratio of 14.7:1,76% mechanical efficiency, and 29% thermal efficiency. The fuel might becurrent available pump fuel M&E 15 & reformulated gasoline. Otherversions of the engine might use M&E 85 Liquid Propane or CompressedNatural Gas. It will of course be appreciated that other engines havingvarying features might be used in keeping with the principles of theinvention.

Alternator/starter and Engine Cooling System

As shown in FIGS. 4 and 5A, the rotor 102 of the preferred embodiment isconstructed of a steel hub 112, which is taper fit to the balance shaft100. Separate, high coercivity, permanent magnets 114 are evenly spacedand adhesively bonded to the periphery of the rotor 102. The magnets 114are further retained against the centrifugal forces by a shrink fitnonmagnetic band 116. It is appreciated that other processes can be usedin addition to the shrink fit to install the nonmagnetic band 116. Themagnets 114 of the rotor 102 are preferably magnetized in place as anassembly.

The stator 96 is preferably constructed of die punched, steellaminations stacked on a mandrel and axially welded on the outsidediameter of a core to form a lamination winding stack 96a of the stator96. In one embodiment, the material of the laminations is a 29 gauge,high grade, non-oriented silicon steel. It is appreciated that thelaminations can be made of any other type of gauge, or grades ofmaterial. A three phase winding, preferably copper or aluminum wire, iswound in slots insulated with high temperature, dielectric insulatingmaterial to form the stator winding. It is appreciated that any othernumber of phase windings can be used in the present invention. Thewinding assembly is impregnated with a high temperature and highstrength epoxy resin, selected to provide protection against an oilcooling environment, which includes entrained moisture and other enginelubricating oil contaminants. Oil cooling allows the alternator/starter86 to be completely sealed and eliminates concern about highly variableair cooling contaminants.

The stator 96 is secured to the combustion engine 84 by piloting thestator 96 between an alternator/starter frame enclosure casting 126 andan engine gear case cover 124 so as to maintain clearance between thestator 96 and rotor 102. A plurality of gaskets 125 are sealed betweenthe alternator/starter frame enclosure casting 126 and the gear casecover 124 so that no cooling oil leaks into the alternator/starter 86.Two stator winding end turns 96b, 96c are located at each end of thewinding stack 96a. The alternator/starter frame enclosure casting 126and the gear case cover 124 are provided with a plastic coolingdistribution end cap 127 around each of the stator winding end turns96b,96c. A cooling oil passageway 250 allows cooling oil flowing from anoil inlet 252 into an annulus 254 around the end turn 96b through anopening 256 of the cooling distribution end cap 127. The cooling oilpassageway 250 also allows the cooling oil to flow across the back ofthe stator stack 96a and into another annulus 258 around the end turn96c on the opposite side through an opening 260 of the coolingdistribution end cap 127. The cooling oil flows along the annulus 254and 258 to the bottom exits 262 and 264 of the cooling distribution endcap 127. Along the passageway 250 across the back of the stator stack96a, there is also an inner annulus 128 which is disposed between thepassageway 250 and the stator stack 96a. The passageway 250 is definedas an oil pipe 255, which connects with the two cooling distribution endcaps 127 on either end of the machine. The oil pipe 255 also includes aplurality of holes 266 along the passageway across the stator stack 96aso that a portion of cooling oil flows through the holes 266 into theannulus 128.

FIG. 5B also shows a cross-sectional view of the annulus 128 with oilflowing from one of the holes 266 and flowing out into a collecting sump128a at an exit 270. The annulus 128 is sized so that the cooling oilfills the annulus 128 so as to effectively transfer the heat from thestator stack 96a.

FIG. 5C shows a cross-sectional view of the annulus 254 around the endturn 96b. The cooling oil flows into the opening 256, along the annulus254, and out of the opening 262. Then, the cooling oil is collected inthe sump 128a. It is appreciated that a similar cross-sectional view isshown regarding the annulus 258 around the end turn 96c.

FIG. 5D shows an enlarged cross-sectional view of FIG. 5A. FIG. 5E showsan enlarged cross-sectional view in FIG. 5A being transactionallyrotated 45 degrees. The cooling oil in the annulus 128 is sealed betweenthe cooling distribution end cap 127 and the alternator/starter frameenclosure casting 126. Accordingly, no cooling oil in the annulus 128leaks into the alternator/starter 86. Further, the annulus 254 and 258are sealed by the cooling distribution end cap 127 and the windings areimpregnated with a high strength epoxy resin, which prevents oil fromleaking into the alternator/starter 86. Thus, there is no oilcontamination introduced into the interior of the alternator/starter 86.

Alternatively, another embodiment of the alternator/starter 86 is shownin FIG. 5F, which is similar to the preferred embodiment shown in FIG.5A. The design of this alternator/starter 86 cooling system is thereverse of that described in FIG. 5A so that an oil inlet 372 is locatedat the bottom of the alternator/starter frame enclosure casting 374. Onesingle annulus 376 is disposed around end turns 378, 379 and alsodisposed between the back of stator stack 380 and the alternator/starterframe enclosure casting 374. The cooling oil flows into the annulus 376around the end turns 378, 379 on each side of the stator 382 and aroundthe back of the stator stack 380, and then the pressurized cooling oilrises into a collecting sump 384. The cooling oil then flows out of anoutlet 386. This reversed cooling oil configuration in the secondembodiment simplifies the design of the alternator/starter 86.

In the second embodiment, the annulus 376 is also sealed from theinterior of the alternator/starter 86 by a plurality of gaskets 325,which are disposed between the alternator/starter frame enclosurecasting 374, the engine gear case cover 388, and the stator stack 380.Further, the windings at the end turns 378,379 are impregnated with ahigh strength epoxy resin which prevents oil from leaking into thewindings or into the alternator/starter 86. Thus, no cooling oil leaksinto the inside of the alternator/starter 86.

FIG. 5G shows a cross-sectional view of the annulus 376. The annulus 376is also sized to ensure that the cooling oil contacts the back of thestator stack 380 so as to effectively transfer the heat from the statorstack 380.

Furthermore, oil cooling allows the alternator/starter 86 to becompletely sealed and eliminates concern about highly variablecontaminants normally carried in the cooling air for an air cooledalternator/starter. Further, the oil flow passing through the annulus issealed to prevent high viscous drag from the oil entering the air gap.

Illustrated in FIGS. 7A,7B is a schematic of a thermal management system201.

In the embodiment shown in FIG. 7A, the alternator/starter 86 is oilcooled. The engine 84 is primarily cooled by cooling water, and to anextent, the engine is cooled by the lubricating oil as well. The coolingoil for the alternator/starter 86 is usually required to be much coolerthan the lubricating oil for the engine 84, so that an auxiliary heatexchanger 390 is used to further cool the cooling oil before it flowsinto the alternator/starter 86.

In the embodiment shown in FIG. 7A, the cooling oil 270 flows from theauxiliary heat exchanger 390, cools the alternator/starter 86, andcollects in a sump 211. Another oil flow 272, without passing throughthe auxiliary heat exchanger 390, is pressurized or sprayed into variouspositions 274 in the engine 84. The oil from the engine 84 also dropsinto the collecting sump 211. The collected oil is scavenged into asuction tube 276 by a pump 278 and is transferred to an external heatexchanger 280 and a heat exchange bypass 282, which allows the oil tobypass the heat exchanger 280 under cold conditions. Then, the coolingoil is circulated and split into two paths, one path for the enginelubrication and cooling, and another path for the alternator/starter 86passing through the auxiliary heat exchanger 390.

In the embodiment shown in FIG. 7A, a wet sump 211 is used. It will beappreciated that a dry sump might be used as shown in FIG. 7B. By usingthe dry sump 500, the size of the dry sump 500 can be dramaticallyreduced because the power of the pump 278 is large enough to scavengethe oil immediately so that almost no oil will be retained in thecollecting sump 211. Because of the reduced size of the collecting sump211, the height of the engine 84 can be dramatically reduced. Since theoil is transferred rapidly in the dry sump design, an oil reservoir 284is placed into the circulated path between the heat exchanger 280 andthe split of the oil path. A pump 286 pressurizes the cooling oil fromthe oil reservoir 284. The cooling oil is then split into two paths, onepath for the engine 84, and another path for the alternator/starter 86passing through the auxiliary heat exchange 390. The pressure of thecooled oil is regulated by an oil regulating valve 288.

In FIG. 7C, there is shown a second embodiment of the oil flow path 210according to FIG. 5F, the oil flow 270 flows into the bottom of thealternator/starter enclosure casting 374 and flows out at the top of theenclosure casting 374.

In operation, the external cooling circuit flow will be bypassed underconditions of high flow restriction (cold starts) and modulated whencooling requirements are low. A preferred embodiment will have aprovision for up to two piston cooling jets per cylinder. Thealternator/starter oil circuit is in parallel with the engine coolingand lubricating oil circuit. Oil cooled to the desired temperature bythe oil to air heat exchanger 280 and the auxiliary oil to air heatexchanger 390, enters the alternator/starter enclosure casting 126 (374in the second embodiment) and is directed over the stator winding endturns 96b,96c (378,379 in the second embodiment) and the back of thestator stack 96a (380 in the second embodiment) by the annulus254,258,128, respectively. The oil then exits at the collecting sump128a (384 in the second embodiment) of the alternator/starter assemblyat a temperature of approximately 95 degrees Centigrade. The oil flowmass is maintained at roughly 3.6 Kg/min (4.3 Liters/min volumetricflow) and is required to maintain safe alternator/starter operatingtemperatures under a maximum alternator/starter loss of approximately2.3 kW (about 93 percent efficiency) at rated speed and power.

Also illustrated in FIGS. 7A,7B is a water cooling system 203, whichincludes a gear driven water pump 205. The water enters a cylinder head207 and exits from an engine crankcase 209. This flow configurationallows a higher compression ratio with its attendant engine efficiencyincrease, due to the lower cylinder head temperature.

Noise, Vibration, and Harshness (NVH) Control Systems

In order to minimize the noise created by the hybrid electric vehicle,the following four steps need to be taken:

1) reducing the overall noise level;

2) improving sound quality by shaping the noise frequency spectrum andeliminating individual offensive frequencies;

3) lowering APU noise levels while the vehicle is moving slowly orstopped with engine speed management; and

4) minimizing the vehicle re-amplification of noise by treating the APUand vehicle as a system.

For illustration and clear explanation purposes, FIG. 6B shows a graphof noise level vs. frequency. The top line (a) illustrates APU enginenoise without a noise control system. A line (b) illustratesapproximately 20-22 dB of noise level reduction due to the noise levelcontrol system. The noise level control system includes a muffler 400,an induction silencer 115, an APU enclosure 150 lined with acousticalmaterial 603, a ventilation inlet duct 152 lined with acousticalmaterial 602, and ventilation outlet duct 154 lined with acousticalmaterial 602 (see FIG. 6A). Thus, the noise level is dramaticallyreduced by the noise level control system.

FIG. 6B also shows a third line (c) having a dramatic noise levelreduction at low and high frequencies. This shaping of the soundfrequency spectrum greatly improves sound quality even though theamplitude of the noise level is almost the same as the second line whichit crosses. To improve the sound quality at higher frequencies, exhaustsystem shell noise sources are attenuated, which include an exhaust gastube 402, an exhaust gas manifold 404, the muffler 400, a catalystconverter 160, and a flex section 406. In addition, the stiffness ofvarious engine surfaces is increased to help improve the sound qualityat the higher frequencies. Further, the acoustical material 600 in thehousing of ventilation inlet duct 152 and the ventilation outlet duct154 significantly attenuates the higher frequency noise to help improvethe sound quality as well. Also acoustical material inside the enclosure150 lowers noise levels. To improve the sound quality at lowerfrequencies, the induction silencer 115 is used. Also, stiffening of thenoise enclosure to raise its natural frequency lowers low frequencynoise levels. The induction silencer 115 is mounted onto an inductionmanifold 106 of the APU 80 as shown in FIG. 6A.

Further, noise levels at some individually offensive frequencies arereduced with the APU noise control system. FIG. 6C shows noise levelsplotted in a frequency domain. Comparing the top and bottom graphs, thenoise levels at frequency area A in the bottom graph are much less thanthe corresponding frequency area A in the top graph. The inductionsilencer lowers the noise levels in frequency area A.

The noise levels at frequency area B in the bottom graph are much lessthan the corresponding frequency area B in the top graph. These noiselevel reductions at the frequency area are due to the contribution ofthe exhaust shell noise sources including the exhaust gas tube 402, theexhaust gas manifold 404, the muffler 400, the catalyst converter 160,and the flex section 406 shown in FIG. 6A. The elimination of otherindividual offensive noises such as parts in resonance will also beneeded to optimize sound quality.

To clearly explain how to meet vehicle interior noise goals, a graph ofinterior noise level (dB) vs. vehicle speed (mph) of a typical vehicle,such as '93 Caravan, is shown in FIG. 6D. The vehicle interior noisedecreases when the vehicle speed decreases. However, at that time, withthe APU engine at 5500 RPM the noise level might be significant eventhough it is lower than the vehicle interior noise when the vehicle isrunning at a high speed. Thus, reducing the APU engine noise evenfurther becomes a goal of reducing the entire vehicle interior noise.

With the APU engine running at 5500 RPM, the interior vehicle noiselevel is in a range of 50-60 dBA, and when the APU engine running speedis 2800 RPM, the interior vehicle noise level is in a range of 40-45dBA. In this embodiment, the APU speed range for proper voltage andcurrent regulation is from 2800 RPM up to 5500 RPM. Therefore, the APUgenerated interior noise levels are in a range between 40-60 dBA. It canbe seen from FIG. 6D that the APU engine noise is not audible until thevehicle speed is reduced to approximately 15-25 mph. In order to lowerthis APU engine noise, the APU engine running speed is changed to 2800RPM whereby the noise level (40-45 dB) is lower than the vehicleinterior noise. As a result, through adjusting the APU engine speed, thevehicle interior noise level is not influenced by the APU engine noise.

With the hybrid electric vehicle stopped in a crosswalk situation, thenoise level and tone from APU running at higher speeds may cause somepeople to be alarmed. In a crosswalk situation, people expect cars tohave idling engines with appropriate noise levels and tone. For clearexplanation purposes, a graph of exterior noise level (dB) of a typicalvehicle, such as '93 Caravan, is shown in FIG. 6E.

To control exterior noise level, sound quality and tone, the APU's speedand load may be changed or the APU stopped. Specifically, the unit mayoperate with or without load between 2800 RPM and 5500 RPM, without loadfrom 2800 RPM to idle speed or be completely stopped for exterior soundcontrol reasons. The loaded speed range is determined by voltage andcurrent control capability. The quoted speed range is expected typicalperformance. Typically, when the APU engine running speed is 5500 RPM,the exterior noise level is in a range of 70-75 dB, and when the APUengine running speed is 2800 RPM, the exterior noise level is in a rangeof 60-65 dB, which are both higher than the normal vehicle exteriornoise level. In one embodiment, the APU engine is shut off so that noaudible noise is created by the APU engine.

The last step is to minimize the vehicle noise level as a system. Afterthe APU 80 is installed into the hybrid electric vehicle, the APU mayexcite mechanical and acoustic resonances in the vehicle itself. Theseresonances can re-amplify the previously attenuated noise or vibrationto a problem level. In addition, sound energy can be converted by amechanical resonance to vibration. Also, vibration by a resonance can beconverted to sound. With knowledge of the vehicle resonances, the APU 80can be designed to minimize the sound or vibration input at theseresonant frequencies. The method to do this, in one embodiment, is thesame strategy of optimizing the spectrum on an individual frequencybasis as discussed before.

The vehicle vibration generally comes from the following four sources:

1) the APU engine vibrations;

2) imbalanced gears, shafts, alternator, or other system partsgenerating vibrations;

3) vibration of the APU enclosure 150 from acoustic and mechanicalexcitation; and

4) re-amplification generated by the resonance of the vehicle itself orthe attachment structure.

FIG. 10 shows these four vibration sources. The letter "s" stands fornoise sources or noise sources transferred from various vibrationsources. The letter "v" stands for vibration sources or vibrationsources transferred from various noise sources. S1 is the noise from theAPU engine intake. S1 can also be transferred to V1 through resonance ofvarious mechanical parts in the vehicle body. S2 is the noise from theAPU engine exhaust system. S2 can also be transferred to V2 throughresonance of various mechanical parts in the vehicle body. S3 is noisefrom the other APU engine parts, and S3 can also be transferred to V3through resonance of various mechanical parts in the vehicle body. V4 isvibration from the engine itself, and V4 can be also transferred tosound S4 through resonance of various mechanical parts in the vehiclebody.

To reduce the APU engine vibrations, there is shown in FIG. 2 a net zeroangular momentum system. In FIG. 2, the auxiliary power unit 80 hasportions of the housing 82 removed. A first gear 88 is driven by acrankshaft 90 of the combustion engine 84. A counter rotating enginespeed balance shaft 100 is disposed alongside the crankshaft 90. Asecond gear 98 is mounted on the balance shaft 100 for engagement withthe first gear 88 on the crankshaft. The first gear 88 causes thebalance shaft 100 and the crankshaft 90 to rotate in opposite directionupon rotation of the crankshaft 90. The rotor 102 of thealternator/starter 86 is mounted on the end of the balance shaft 100 forrotation therewith. In the preferred embodiment, the alternator/starter86 functions to charge the electric vehicle's batteries and also as astarter for starting the engine 84. Two balance weights 104 areselectively sized and positioned on the counter rotating balance shaft100 so as to effectively cancel primary rotating couple of the auxiliarypower unit 80 due to reciprocating motion of the pistons 107 and rods105 shown in FIG. 3. Additionally, a net angular momentum of allrotation components in the auxiliary power unit 80 is zero, resulting ina zero vibratory roll torque acting on the auxiliary power unit 80.These vibratory roll torques are typically caused by such things aspiston thrust and bearing reaction forces, alternator/starter torquepulses, starter torque pulses, etc. Therefore, the auxiliary power unit80 exhibits substantially no vibratory roll motion. The crankshaft andbalance shaft create equal inertia counter rotating systems that cancelall vibratory roll torque impulses including those encountered duringstartup, shutdown, and transient operating condition. Thus, thevibration V4 and noise S4 created by the APU engine are minimized.

To minimize the vibrations from the imbalanced gears, shafts,alternator, or other system parts, the engine exhaust system and enginemounting structure are specifically designed. In one embodiment, a setof rubber vibration isolators 502 are used in the engine mountingstructure. It is appreciated that any other type of vibration absorbingmembers 504, such as springs, can be used. A detailed discussion of thestructure of the engine exhaust system flex section will be providedlater. The "six" rigid body mode natural frequencies of this mountingsystem are designed to be in the 8-10 Hz frequency range for high levelsof vibration isolation.

To minimize the vibrations transmitted from the APU enclosure 150 to thevehicle itself, a set of rubber vibration isolators 504 are used in theAPU mounting structure. It is appreciated that any other type ofvibration absorbing member, such as springs, can be used. The mass ofnoise enclosure 150 between the two vibration isolation systems enablesthe two vibration isolation systems to simultaneously isolate vibration.

The mass of the enclosure 150 plus attached parts typically must beabout 10% of the engine/alternator mass for good "dual" isolation systemperformance. To minimize the vibration re-amplification generated by theresonance of vehicle or mounting structure, the APU enclosure 150 andother mounting parts are specifically designed. A detailed discussionwill be provided later.

Harshness is usually characterized by people's reaction to noise andvibration from various sources. In this case, it is the people'sreaction to noise and vibration generated by the hybrid electric vehicleAPU. The harshness is well controlled by dramatically reducing the noiseand vibration as discussed before.

In one embodiment shown in FIG. 6A, the integrated auxiliary power unit80 is installed in an enclosure 150 and is connected with otherancillary systems so as to form an auxiliary power system having noise,vibration, and harshness control. The stiffness of the enclosure 150 isusually designed to meet the requirement of the noise and vibrationcontrol with the enclosure specifically designed for specific naturalfrequencies. A plurality of ribs are molded to strengthen the stiffnessof a top cover 150a of the enclosure 150. Two couples of cross ribs 420are disposed at inside walls parallel to the edges of the enclosure 150.In addition, a plurality of ribs 422 are disposed at the inside bottomof a bottom container 150b of the enclosure 150. The ducts may also havethe same type of stiffening ribs 600.

A high performance vibration isolation system also includes theinduction silencer 115 which reduces the low frequency acousticexcitation of the enclosure 150. The enclosure 150 is in turn isolatedfrom the vehicle with a second isolation system so that sound inducedexcitation of the enclosure is not transmitted into the vehicle body.The flex section may be placed at the vibration isolation system rollcenter to further reduce the vibration transmitted through the exhaustsystem.

The flex section 406 in the exhaust system after the catalytic converter160 will isolate exhaust system vibration from the vehicle body.

In one embodiment, the enclosure 150 might be formed by existing enginecompartment surfaces which have been suitably acoustically treated. Inyet other embodiment, the enclosure 150 might be open to the pavementbelow.

The exhaust noise is preferably attenuated by about 50 to 60 dB with amuffler. Induction noise is attenuated by about 10 to 22 dB with theinduction silencer 115. The ducts 152 and 154 lined with the acousticalmaterial 600 attached to the ventilation openings 424 of the enclosure150 attenuates the noise to the same level as the enclosure 150 whichhas 22 dB of attenuation. The ducts may include a 90° or greater bendfor further noise reduction by blocking line of sight noise.

Proper execution of intake, exhaust and enclosure noise attenuationsystems will preferably result in uninstalled auxiliary power unit 80having noise levels of approximately 70-76 dBA @1 meter for 2800 RPM and83-88 dBA @ 1 meter for 5500 RPM.

Further in FIG. 6A, an enclosure ventilation fan 158 is located in theenclosure 150 near the end of ventilation inlet duct 152 for thermalmanagement. Thus, outside ambient cooling air is blown into theauxiliary power system 80 so as to reduce the high temperature therein.Warm air is vented out the exhausted gases outlet duct 154.

Emissions/Fuel Economy Systems

The auxiliary power unit 80 will meet 1997 ULEV emission standards. Theemission control system incorporates both inlet port induced air motionand compression induced turbulence for fast and complete combustion. Theexhaust will be passed through a close coupled supplementary heated ifnecessary, 3-way catalytic converter 160 to maximize emission conversionefficiency. Supplementary air to the converter 160 will be provided ifrequired. A closed loop control of the sequential port fuel injectionsystem will be used for optimum stoichiometric air-fuel ratio control.It is appreciated that as "lean burn" 3-way catalytic convertertechnology is perfected, air/fuel ratios considerably leaner thanstoichiometric (14.7:1) will be incorporated to further reduce fuelconsumption. Electronically controlled exhaust gas recirculation will beused to minimize oxides of nitrogen-NOx (x=1, 2, 3, 4, etc.) productionin the combustion process.

FIG. 8 shows a block diagram of a hybrid electric vehicle which hasbatteries 508 providing electrical power to the vehicle electrictraction motors 144. The batteries 508 can be recharged either by anexternal energy source 146, such as the electric utility grid, or by thealternator/starter 86 through an inverter 30. The alternator/starter 86is driven by the combustion engine 84 which uses combustible fuel suchas gasoline, diesel, CNG (compressed natural gas), LPG (liquid petroleumgas), M/E 85 (methanol/ethanol 85), etc. The auxiliary combustion engine84 is started by the alternator/starter 86 when a vehicle master controlunit 172 (shown in FIG. 11) senses that the batteries 142 need charging.

It is anticipated that the operating modes of an HEV will entail,operation at various power levels, speeds and periodic stop/startcycles. By utilizing cylinder shut down and RPM (speed) control, fueleconomy, emissions, and NVH (noise vibration harshness) can be minimizedat various real world driving conditions.

To minimize emissions during start cycles, the catalytic converterpre-heating can be employed. To minimize fuel conditions at part loaddemands, cylinder shut down and RPM reduction can be employed. This canbe accomplished without any increase in NVH by the use of zero netangular momentum balancing as mentioned before.

APU Battery Charging System

The APU 80 includes the APU master control unit 518 which charges thevehicle battery 508 when the vehicle needs more power. The APU 80includes the inverter 130 electrically connected to thealternator/starter 86. The APU master control unit provides a maximumcontinuous thirty-five kilowatts power output controlling output currentfrom the alternator/starter 86 in a battery charging power loop 512. TheAPU master control unit 518 is also designed to utilize battery voltageprovided by the electric vehicle's batteries to provide an estimatedsixty foot pounds APU engine cranking torque to the crankshaft 90required to start the combustion engine 84 in an engine start speed loop510. Once the APU engine 84 is started and runs up to about 600 RPM, theAPU master control unit 518 disconnects the engine start speed loop 510,and connects to the battery charging power loop 512 to charge thebatteries by using the electricity generated from the alternator/starter86. FIG. 12 shows a plot of APU engine speeds at different time (a,b,c)during the cranking cycle. The explanation is as follows:

1) To increase engine speed from 0 to about 600 RPM (a), the invertercurrent loop reference is obtained from the start speed loop 510 to usethe battery power to start and run the APU engine 84 to a minimumrunning speed, such as 600 RPM in the embodiment. It is appreciated thatthe minimum running speed can be changed according to different APUengine designs or starting criterion.

2) When the APU engine speed is 600 RPM, there is usually a short periodof engine adjusting time (a-b). It is appreciated that this period ofengine adjusting time will vary according to different APU enginedesigns.

3) When the APU engine speed further increases, the inverter currentloop is disconnected from the start speed loop 510, and then the systemis connected to the battery charging power loop 512. At this time, theAPU engine 84 and the alternator/starter 86 creates electricity tocharge the same batteries which are used to start and run the APU engine84 in (1).

4) In one embodiment, the maximum APU engine speed is about 5500 RPM(c). The minimum normal APU engine running speed which meets the batteryrequirement is about 2800 RPM. It is appreciated that the maximum andminimum APU engine speeds can be adjusted according to different APUdesigns.

5) The APU master control unit 518 is also used to adjust the APU enginespeed as required. For example, as discussed before, the APU enginespeed needs to be reduced from 5500 RPM to 2800 RPM to prevent excessiveinterior and exterior vehicle noise at slow vehicle speed or while thevehicle is stopped.

Further, there is an initial APU engine crankshaft position detectingprocedure before the inverter system starts the APU engine 84. Thedetailed description of this initial engine position detecting procedurewill be discussed later.

The inverter 130 of the APU master control unit 518 is electricallyconnected to the three alternator/starter phases so a three-phasecurrent output is produced by the inverter 130 in the APU master controlunit 518 using alternator/starter inductance as a current filter. FIG. 9shows an electrical schematic graph of the inverter 130. There are shownthree transistor legs parallel to each other. Each transistor leg hastwo transistors in series electrically connected to a common node,designated reference numbers A,B,C, respectively. For explanationpurpose, the upper transistors are named A1,B1,C1, and the lowertransistors are named A2,B2,C2, respectively. The common nodes A,B,C areelectrically connected to alternator/starter back emf FA,FB,FC throughinductors LA,LB,LC, respectively. In each transistor, the collector nodeis electrically connected to the emitter node through a one-way diode.The emitter node of each transistor is electrically connected to sixisolated outputs of a drive amplifier device 516 of the APU mastercontrol unit 518. The drive amplifier device 516 has six isolated driveamplifiers each of which has an isolated voltage reference node. Thelogic output of each isolated drive amplifier provides an "on" or "off"logic signal to the gate node of each transistor. The voltage referencenodes are electrically connected to the emitter node of each transistor.The APU master control unit controls the gate node of each transistor sothat each transistor series connected set has one transistor in an "on"status and the other transistor in an "off" status. The APU mastercontrol unit 518 also controls at least one upper transistor, A1,B1,C1,and one lower transistor, A2,B2,C2, in an "on" position. Thesetransistor sets are further electrically parallel connected to thevehicle batteries. A filter capacitor CR is used across the inverterpositive and negative rails to filter out current spikes and prevent thespikes from reaching the vehicle battery as shown in FIG. 9.

At the APU engine start time, the inverter 130 discharges the batteriesand converts DC voltage of the batteries to a three-phase AC voltage atan output node 425. Thus, the alternator/starter 86 is used to apply thecranking torque to the APU engine crankshaft 90. Then, the fuel andignition systems are energized to start the engine. The fundamentalfrequency of the inverter 130 at the three-phase output node determinesthe speed of APU engine 84. Once the APU engine speed increases to apredetermined speed, the alternator/starter 86 switches to the batterycharging power loop 512 so that the inverter 130 converts the ACcurrents from the three alternator/starter phases 514 to DC current forcharging the batteries.

The APU Master Control Unit 518 controls the APU master control unit 518and engine starting system. FIG. 13 shows a block diagram of the APUmaster control unit 518 which is controlled by the APU Master ControlUnit 518. The battery charging procedures are as follows:

1) The APU Master Control Unit 518 sends a command to the inverter 130to set the common node A a positive DC current, set the common node B anegative DC current, and set the common node C to zero current. Thus,the position of the APU engine crankshaft 90 is switched to a knownposition which is sensed by an encoder sensor (not shown) mounted on thecrankshaft 90. The DC current is large enough to force the crankshaft 90to the desired position in the presence of friction forces.

2) The APU Master Control Unit 518 sends an S_(ref) signal to commandthe engine start speed loop of the APU master control unit 518. Thedrive amplifier system 516 sends logic signals to the six inverter 130switches. The inverter 130 then converts the batteries' DC voltage to ACvoltage so as to drive the alternator/starter 86 crankshaft.

3) When the engine fires and speeds the crankshaft up to exceed 600 rpm(for example), the APU master controller disconnects the engine startspeed loop 510 (a). The battery charging power loop 512 (b) is connectedbut is commanded to provide zero power until the crankshaft speedreaches command speed (5500 rpm (c) for example). DC voltage and currentis used to provide the previous output power information. Therefore,when the vehicle's need for power changes, the difference between thepresent required power and the previous power can be determined, and theAPU power provided can be adjusted accordingly. The APU engine speed maybe varied if the battery charging power changes significantly.

In the embodiment, the vehicle batteries are 350 V. It is appreciatedthat voltage of the batteries can be chose by the industry requirement.

Additional alternator/starter specifications might include thefollowing:

Type: Permanent Magnet

No. Poles: 12

Magnet: Neodymium Iron Boron, 27 Megagauss oerstad Energy Product

Winding: 3 Phase wye

Stator OD: 6.5 inches

Stator Material: M-19, 29 gauge electrical steel

Insulation/Temp.: Class H+, 125 degree Celsius maximum rise byresistance

It will be appreciated that the above is a detailed description of anembodiment of the alternator/starter 86 which might be used in thepresent invention. It will be appreciated that other embodiments ofalternator/starters might be used with the present invention.

Vehicle Control System

As illustrated in FIG. 11, an Auxiliary Power Unit (APU) Master ControlUnit 518, a permanent magnet Alternator/Starter Controller 166, and anElectronic Engine Controller 168 are included in a vehicle controlsystem 172. The APU Master Control Unit 518 is microprocessor based andis the APU coordinator communicating with the Electronic EngineController 168, the Alternator/Starter Controller 166, and a ThrottleActuator 170. In addition, the APU Master Control Unit 518 alsocommunicates status back to the Master Control Unit 172 of the hybridelectric vehicle. Upon starting the vehicle, the vehicle Master ControlUnit 172 sends a power-up command to the APU Master Control Unit 518.The APU Master Control Unit 518 initiates the engine start speed loop110 and brings the engine 84 up to speed using an electronicallyactuated throttle plate (not shown). The vehicle Master Control Unit 172establishes a desired power level and sends a power command to the APUMaster Control Unit 518. The APU Master Control Unit 518 sends a powerlevel command to the Alternator/Starter Controller 166 once thecombustion engine 84 is up to a proper speed. Signals fed back from theAlternator/Starter Controller 166 to the APU Master Controller Unit 518are voltage, current, operational status, and diagnostics information.Signals from the combustion engine 84 to the APU Master Control Unit 518via the Electronic Engine Controller 168 are engine crankshaft position,throttle position, operational status, and diagnostics information.Signals back from APU Master Control Unit 518 to the vehicle MasterControl Unit 172 are voltage, current, operational status, anddiagnostics information. Alternator/Starter and Engine Controller 166commands from the APU Master Control Unit 518 are derived by acombination of look-up tables and controller logic.

The Electronic Engine Controller 168 works as it does in today'sautomobiles where the Electronic Engine Controller 168 controls engineoperating parameters to ensure low emissions and maximum performance.

The Alternator/Starter Controller 166 is a three-phase inverter whichprovides cranking current and also controls the alternator/starteroutput power. The three phase inverter is bi-directional and will forcethe currents flowing in the three phases of the alternator/starter to besinusoidal and in phase with the back emf for most situations. It may benecessary to vary the phase angle between the alternator/starter backemf and phase current depending on operating conditions. Filtering isprovided on the DC output so inverter switching noise does not adverselyaffect the electrical traction drive or batteries. TheAlternator/Starter Controller 166 is self protecting against i) overvoltage, ii) under voltage, iii)over current, and iv) over temperature.It is fused on both the three-phase input and DC output to preventdestruction of other hybrid electric vehicle subsystems (e.g. batteries)in case of an internal fault.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size and arrangement of parts within the principles of the invention tothe full extent indicated by the broad general meaning of the terms inwhich the appended claims are expressed.

What is claimed is:
 1. A noise, vibration, and harshness control systemfor a hybrid electric vehicle having an auxiliary power unit,comprising:an auxiliary power unit enclosure containing the auxiliarypower unit for reducing a noise level of the auxiliary power unit; aninduction silencer for separating noise and vibration of the auxiliarypower unit to the enclosure so that sound quality of the hybrid electricvehicle is increased, the induction silencer being mounted onto aninduction manifold of the auxiliary power unit; auxiliary power unitexhaust means for reducing noise and vibration from an exhaust manifoldof the auxiliary power unit, the auxiliary power unit exhaust meansbeing connected to the exhaust manifold and being mounted onto theenclosure; means for ventilating air in the enclosure, the ventilatingmeans being at least partially contained in the enclosure; and whereinthe auxiliary power unit enclosure includes a top cover having aplurality of cross ribs inside the top cover, and a bottom containerhaving a plurality of cross ribs inside the bottom container.
 2. Anoise, vibration, and harshness control system in accordance with claim1, wherein the auxiliary power unit exhaust means includes a first ductand a pipe at least partially retained in the first duct, the pipe beingconnected to the exhaust manifold at one end, the pipe having a flexsection and a catalyst converter section so that an exhaust fuel passingthrough the catalyst converter section and the flex section to a mufflerat a second end of the pipe.
 3. A noise, vibration, and harshnesscontrol system in accordance with claim 2, wherein the first ductincludes walls which are made of an acoustic material so as to reducethe noise and vibration from the exhaust manifold.
 4. A noise,vibration, and harshness control system in accordance with claim 2,wherein the flex section is interconnected to the catalyst convertersection.
 5. A noise, vibration, and harshness control system inaccordance with claim 1, wherein the ventilating means includes a secondduct for reducing the noise and vibration generated from a ventilationfan which is mounted onto the second duct, the second duct includingwalls which are made of an acoustic material. power unit, comprising:anauxiliary power unit enclosure containing the auxiliary power unit forreducing a noise level of the auxiliary power unit; an inductionsilencer for separating noise and vibration of the auxiliary power unitto the enclosure so that sound quality of the hybrid electric vehicle isincreased, the induction silencer being mounted onto a fuel ignitioninduction manifold of the auxiliary power unit; auxiliary power unitexhaust means for reducing noise and vibration from an exhaust manifoldof the auxiliary power unit, the auxiliary power unit exhaust meansbeing connected to the exhaust manifold and being mounted onto theenclosure; and means for ventilating air in the enclosure, theventilating means being at least partially contained in the enclosure.6. A hybrid electric vehicle driven by a battery unit, comprising:anauxiliary power unit for charging the battery unit, the auxiliary powerunit including an engine and an alternator/starter; alternator/starteroil cooling means for cooling alternator/starter of the auxiliary powerunit; thermal management means for cooling and lubricating engine of theauxiliary power unit; noise, vibration, and harshness control means forreducing noise and vibration generated by the auxiliary power unit, thenoise, vibration, and harshness control means comprising: an auxiliarypower unit enclosure containing the auxiliary power unit for reducing anoise level of the auxiliary power unit; an induction silencer forseparating noise and vibration of the auxiliary power unit to theenclosure so that sound quality of the hybrid electric vehicle isincreased, the induction silencer being mounted onto an inductionmanifold of the auxiliary power unit; auxiliary power unit exhaust meansfor reducing noise and vibration from an exhaust manifold of theauxiliary power unit, the auxiliary power unit exhaust means beingconnected to the exhaust manifold and being mounted onto the enclosure;and means for ventilating air in the enclosure, the ventilating meansbeing at least partially contained in the enclosure; wherein theauxiliary power unit enclosure includes a top cover having a pluralityof cross ribs inside the top cover, and a bottom container having aplurality of cross ribs inside the bottom container; emission/fueleconomy control means for optimizing emission and fuel used by theauxiliary power unit; and an auxiliary power unit master control unitfor charging of the battery unit in an engine running mode, for startingof the engine in an engine starting mode, and for adjusting an enginespeed of the auxiliary power unit depending on power demanded on theauxiliary power unit so as to prevent excessive noise, vibration, andharshness.
 7. A noise, vibration, and harshness control system for ahybrid electric vehicle having an auxiliary power unit, comprising:anauxiliary power unit enclosure containing the auxiliary power unit forreducing a noise level of the auxiliary power unit; an inductionsilencer for separating noise and vibration of the auxiliary power unitto the enclosure so that sound quality of the hybrid electric vehicle isincreased, the induction silencer being mounted onto an inductionmanifold of the auxiliary power unit; auxiliary power unit exhaust meansfor reducing noise and vibration from an exhaust manifold of theauxiliary power unit, the auxiliary power unit exhaust means beingconnected to the exhaust manifold and being mounted onto the enclosure;means for ventilating air in the enclosure, the ventilating means beingat least partially contained in the enclosure; and wherein the auxiliarypower unit enclosure includes a top cover and a bottom container, theenclosure having rib means for strengthening stiffness of the enclosure.